Microcracked nickel plating bath and process

ABSTRACT

A BATH FOR PRODUCING A MICROCRACKED NICKEL ELECTRODEPOSIT COMPRISING AN AQUEOUS ACIDIC SOLUTION CONTAINING NICKEL IONS; AND AN EFFECTIVE MICROCRACKING AMOUNT OF A POLYAMINE OF THE FORMULA:   (R) (R&#39;&#39;) N-(CH2) A-N (R&#39;&#39;) (R)   WHEREIN R AND R&#39;&#39; ARE INDEPENDENTLY SELECTED FROM THE GROUP CONSISTING OF HYDROGEN, ALKYL OF FROM 1 TO 4 CARBON ATOMS AND HYDROXY SUBSTITUTED ALKYL OF FROM 1 TO 4 CARBON ATOMS; PROVIDING AT LEAST ONE OF R AND R&#39;&#39; IS A HYDROXY ALKYL; AND A IS FROM 1 TO 4.

United States Patent US. Cl. 204-49 32 Claims ABSTRACT OF THE DISCLOSURE A bath for producing a microcracked nickel electrodeposit comprising an aqueous acidic solution containing nickel ions; and an effective microcracking amount of a polyamine of the formula:

wherein R and R are independently selected from the group consisting of hydrogen, alkyl of from 1 to 4 carbon atoms and hydroxy substituted alkyl of from 1 to 4 carbon atoms; providing at least one of R and R is a hydroxy alkyl; and a is from 1 to 4.

: BACKGROUND OF THE INVENTION Various means have been used to impart brilliance and corrosion resistance to metal substrates. One way is to use a nickel electrodeposit on to a metallic substrate followed vby a chromium electrodeposit. The nickel deposit may be ofthe microporous type. .See US. 3,152,971, 2 and: 3. The chromium deposit ,could impart corrosion resistance by microcracking the nickel deposit during or after the deposition of the chromium. In order to impart microcracking to the nickel deposit, it is desirable that the'nickel be deposited in a manner that would cause substantialjmicrocracking;:-This would permit the utilization of present electroplating facilities Without having to utilize additional plating apparatus such as additional tanks and the like. 7

US. 3,563,864 describes a microcracking process wherein during the deposition of the chromium, the microc'rac'ki'ng occurs in the nickel substrate. See also French Pat. No. 1,447,970.

It has now been found that a nickel plating bath may be employed such that the microcracking will occur in the deposition of nickel.

SUMMARY OF THE INVENTION A process is described for electrodeposition of a microcracked nickel deposit employing an aqueous acidic nickel electroplating bath containing an effective microcracking amount of a hydroxy containing polyamine.

DESCRIPTION OF PREFERRED EMBODIMENTS A process is described for electrodepositing a microcracked nickel deposit so that the nickel deposit will microcrack, thereby imparting desirable corrosion resistant properties to the substrate. The electrodeposition of nickel can subsequently be followed by a deposition of other materials such as chromium.

By stressed is meant that the nickel deposit formed during the nickel electroplating will crack due to the internal stresses of the nickel deposit.

By microcracked is meant that the number of cracks per linear inch is quite large, ranging from about 300 to 3,000, preferably 500 to 1,500.

It has been found that the microcracking in the nickel deposit occurs simultaneously as the nickel is deposited. However, in thin deposits of nickel (about 0.1 mil) a higher stressed nickel deposit is obtained (about 12,000 to 20,000 p.s.i. tensile). This is contrasted with the more normal deposition thickness of 1 mil Where the stress in the nickel deposit is substantially zero. Due to the micro- 3,761,363 Patented Sept. 25, 1973 cracking that occurs in the nickel deposit, test ASTM B 456 for microcracked chromium is met when chromium is deposited on top of the microcracked nickel deposit.

The tests for determining a stressed deposit are described in Stress in Electrodeposited Nickel by W. M. Phillips and F. L. Clifton, published in the 34 Annual ProceedingsTechnical Sessions of the American Electroplaters Society (1947), pp. 97-114.

The substrate for the microcracked nickel deposit can be a base metal susceptible to corrosion, such as iron, steel, nickel, nickel-cobalt alloys, cobalt, and the like. In addition, the substrate may also be a plastic material, such as polypropylene, polyethylene, acrylonitrile buta diene styrene (ABS), phenolics, and the like.

The nickel plating bath that may be employed in the present invention is one containing inorganic salts of nickel, and an effective microcracking amount of a bath soluble hydroxy containing polyamine of the formula:

wherein R and R are independently selected from the group consisting of hydrogen, alkyl of from 1 to 4 carbon atoms and hydroxy substituted alkyl of from 1 to 4 carbons; providing at least one of R and R is a hydroxy alkyl; and a is from 1 to 4.

The nickel plating bath normally employed is one that has an acidic pH, preferably ranging from 1 to 6, or even more preferably, 2 to 5.

The temperatures of the bath that may be employed in the present invention is one ranging from 50 to 150 F., preferably 100 to F.

During the deposition of the nickel deposit, agitation or no agitation may be employed. The agitation can take the form of mechanical or air agitation. In the deposition of the nickel deposit on to a plastic substrate, no agitation is preferred.

Suitable polyamines that may be employed in the present invention are ones where R or R, may be as follows: alkyl such as methyl, ethyl, propyl, isopropyl, butyl, and the like; hydroxy substituted alkyl of 1 to 4 carbon atoms, such as hydroxy methyl, hydroxy ethyl, hydroxy propyl, and hydroxy butyl, and the like. Suitable polyamines are those listed below:

The nickel plating bath of the present invention may also contain nickel brighteners such as acetylenic or heterocyclic quaternary amine nickel brighteners, or selected sulpho-oxygen compounds.

When acetylenic nickel brighteners are employed they are used in amounts ranging from about 10 to about 500 mg./l. Suitable acetylenic nickel brightening agents are those described in US. 2,800,440 and US. 3,140,988, such as ether derivatives of alkyne sulfonic acids having from 3 to 14 carbon atoms, condensation products of alkylene oxides, such as ethylene oxide, propylene oxide, epichlorohydrin and acetylenics with replaceable hydrogens, such as propargyl alcohol, butyne diol, and the sulfonate derivatives thereof and the like.

When employing quaternary heterocyclic nickel brighteners, it is preferred that about 10 to about 200 mg./l. may be employed. Suitable quaternary nitrogen heterocyclic compounds are those that are described in US. 3,318,787. Preferred compounds are the pyridine, quinaldine or isoquinoline ring systems. Suitable quaternary heterocyclic compounds are quinaldine propane sultone, quinaldine dimethyl sulfate, quinaldine allyl bromide, pyridine allyl bromide, benzyl chloride quaternary of pyridine or nicotinic acid, isoquinaldine allyl bromide, and the like.

It has been surprisingly found that certain sulfo-oxygen compounds may be employed in amounts ranging from about 0.01 to about 2.0 grams/liter. Normally sulfo-oxygen compounds impart stress reduction to a nickel deposit. Therefore, such compounds as saccharin, aromatic sulfonic acids, sulfonamides, and sulfonimides should not be employed in the present bath. However, such sulfooxygen compounds as the aliphatic sulfonates may be used such as allyl sulfonate, vinyl sulfonate, betastyrene sulfonate, cyano alkane (1 to 4 carbon atoms) sulfonic acid, and the like. The styrene sulfonate is classified here as an aliphatic sulfonate because the sulfonate group is attached to the ethylenically unsaturated side of the chain.

It has also been found that the addition of finely divided powders may be added to the nickel electroplating bath resulting in a desirable nickel deposit and using a lower concentration of the organic nickel brightening addition agents, thereby increasing the microdiscontinuity. Suitable finely divided powders are inorganic materials such as barium sulfate, aluminum oxide, silicon dioxide, and the like. See US. 3,152,971-3 for other suitable powders. The size of these powders range from 0.5 to 4 microns and about 2 to about 50 grams/liter give satisfactory results.

A suitable nickel plating bath that may be employed in the present invention is as follows:

Concentra- Optimum Compound tion range concentration NiSO4, g./l 30-100 NiClz-6HzO, g. 100-400 225 HsBOa, g-/1 25-60 45 pH 1-6 4. 0 Temperature, F 50105 110 Polyamino, g./l 0. -5 0. 1

EXAMPLE I A nickel plating bath was formulated as follows.

The above bath was utilized by electrolyzing the bath with a steel cathode producing 0.1 mil thickness nickel having a dense microcracked deposit, producing 1,200- l,500 cracks per linear inch.

EXAMPLE II The bath of Formula I was used to electrodeposit nickel on to a commercially available phenol-formaldehyde resin material that was molded into a hub cap shape. The phenolic resin substrate was treated to the following pretreatment.

(1) Chromic acid etch CrO-H SO at 80 C. for 5 to 15 minutes.

(2) Clean water rinse with a warm detergent and then clean water rinsed again.

(3) Stannous chloride HCl bath (l0 g./l.) 25 C. for 2 minutes.

(4) Clean water rinse.

(5) Palladium chloride HCl activator (0.2 g./l.) 25 C. for 2 minutes.

(6) Clean water rinse.

(7) Palladium chloride HCl accelerator (5.0 g./l.) 50 C. for 2 minutes.

(8) Electroless nickel deposit C. for 10 minutes.

(9) Bath of Example #1.

EXAMPLE III The process of Example I was followed to deposit a microcracked nickel deposit on to a nickel plated steel panel which was subsequently coated with an electrodeposit of chromium employing normal chromium electrodeposition techniques. The number of cracks per linear inch in the final chrome deposit was about 800 resulting in good corrosion resistant properties.

EXAMPLE IV A Watts nickel plating bath was formulated as follows.

Concentration, grams/liter NiSO -6H O 250-350 NiCl -6H O 30 60 H BO 45 Ethylene diamine tetraethanol 0.1 pH 4.0 Temperature F Using air agitation the above bath was electrolyzed with a steel cathode producing 0.1 mil thickness nickel having a dense microcracked deposit, producing 300-500 cracks per linear inch.

EXAMPLE V Following the procedure of Example I except employing air agitation and 0.05 g./l. of quinaldine propane sultone for the diol/hydrin condensation product, equivalent results were obtained.

EXAMPLE VI On to a formed S-shaped panel, nickel was deposited to a thickness of 0.5 mil from a standard bright nickel electroplating bath, followed by a microcracked nickel strike of 0.15 mil thickness using the bath of Example I.

On this panel was then deposited 0.01 mil of chromium from standard chromium electroplating baths. Dubpernell tests showed a dense microcracked pattern in the high current density areas and virtually no pattern in the low current density areas. To the microcracked nickel bath was then added 2 g./L of fine silicon dioxide powder. The resulting Dubpernell tests showed that a dense microcracked pattern was evident over a wide current density range. Microscopic analysis indicated that the deposit contained a combination of microcracking and microporosity.

What is claimed is:

1. An aqueous acidic bath for producing a microcracked nickel electrodeposit consisting essentially of nickel ions; and an effective microcracking amount of a polyamine of the formula:

wherein R and R are independently selected from the group consisting of hydrogen, alkyl of from 1 to 4 carbon atoms and hydroxy substituted alkyl of from 1 to 4 carbon atoms; providing at least one of R or -R is a hydroxy alkyl; and a is from 1 to 4.

2. The bath of claim 1, wherein the polyamine is present in an amount ranging from about 0.05 to 5 grams/ liter.

3.. The bath of claim 2, further comprising about 0.01 to about 2.0 g./l. of a sulfa-oxygen compound independently selected from the group consisting of aliphatic sulfonates.

4. The bath of claim 3, wherein the sulfonate is allyl sulfonate.

5. The bath of claim 3, wherein the sulfonate is vinyl sulfonate.

6. The bath of claim 3, wherein the sulfonate is beta styrene sulfonate.

7. The bath of claim 3, wherein the sulfonate is cyano alkane sulfonate having up to 5 carbon atoms.

8. The bath of claim 2, wherein R is a hydroxy substituted alkyl.

9. The bath of claim 8, wherein R is a hydroXy substituted alkyl.

10. The bath of claim 2, wherein a is 2.

11. The bath of claim 2, wherein the polyamine is a compound of the formula:

(HQCH CH N (H CH CH N (H) (CH CH OH) 12. The bath of claim 2, wherein the polyamine is of the formula:

13. The bath of claim 2, further comprising about to about 200 mg./l. of a quaternary heterocyclic nickel brightener.

14. The bath of claim 2, further comprising about 10 to about 500 mg./l. of an acetylenic nickel brightener.

15. The bath of claim 1, further comprising fine bath insoluble powders in an amount ranging from about 2 to about 50 grams per liter.

16. A process for producing a microcracked nickel electrodeposit comprising electrolyzing the bath of claim 1 on to a substrate, thereby resulting in a microcracked nickel deposit.

17. The process of claim 16, wherein the bath further comprises about 0.01 to about 2.0 g./l. of a sulfo-oxygen compound independently selected from the group consisting of aliphatic sulfonates.

18. The process of claim 1.7, wherein the sulfonate is allyl sulfonate.

19-. The process of claim 17, wherein the sulfonate is vinyl sulfonate.

20. The process of claim 17, wherein the sulfonate is beta styrene sulfonate.

21. The process of claim 17, wherein the sulfonate is cyano alkane sulfonate having up to 5 carbon atoms.

22. The process of claim 16, wherein the number of cracks per linear inch ranges from. 300 to 3,000.

23. The process of claim 16, wherein the number of cracks per linear inch ranges from 500 to 1,500.

24. The process of claim 16, wherein the polyamine is present in an amount ranging from about 0.05 to 5 g./l.

25. The process of claim 16, wherein R is a hydroxy substituted alkyl.

26. The process of claim 16, wherein R is a hydroxy substituted alkyl.

27. The process of claim 16, wherein a is 2.

28. The process of claim 16, wherein the polyamine is a compound of the formula:

(HOCH CH (H)-CH CH N(H) (CHgCHgOH) 29. The process of claim 16, wherein the polyamine is of the formula:

30. The process of claim 16, wherein the bath further comprises about 10 to about 200 mg./l. of a quaternary heterocyclic nickel brightener.

31. The process of claim 16, wherein the bath further comprises about 10 to about 500 mg./l. of an acetylenic nickel brightener.

32. The process of claim 16, wherein the bath further comprises fine bath insoluble powders ranging in an amount from about 2 to about grams per liter.

References Cited UNITED STATES PATENTS 3,152,971 10/1964 Tomaszewski et a1. 204-41 2,658,867 11/ 1953 Little 204-49 2,800,440 7/ 1957 Brown 204-49 3,471,271 10/ 1969 .Brown et a1. 204-49 X 3,474,010 10/ 1969 McMullen et a1. 20449 X 3,563,864 2/1971 Du Rose et a1 204-49 X FOREIGN PATENTS 871,882 7/1961 Great Britain 20449 GERALD L. KAPLAN, Primary Examiner 

